abort-controller-x-reactive-store
v0.1.0
Published
Reactive store primitive and helpers
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abort-controller-x-reactive-store
Reactive store primitive and helpers.
This is a companion package of
abort-controller-x
.
Installation
yarn add abort-controller-x-reactive-store
API
Store
type Store<T> = {
value: T;
wait(signal: AbortSignal, condition: (value: T) => boolean): Promise<T>;
};
type ReadonlyStore<T> = Readonly<Store<T>>;
A reactive store (a.k.a. reactive variable) holds a value that can be read and updated, and can also be observed by means of waiting for a condition to be met.
The wait
method returns a promise that resolves when the condition is met, or
rejects with an AbortError
if the signal is aborted.
deriveStore
function deriveStore<T, R>(
parentStore: ReadonlyStore<T>,
transform: (value: T) => R,
): Store<R>;
Derives a new store from a parent store by applying a transformation function to its value.
watchStore
async function watchStore<T>(
signal: AbortSignal,
store: ReadonlyStore<T>,
): AsyncIterable<T>;
Allows to react on changes of a store value using async iteration, e.g.:
for await (const value of watchStore(signal, store)) {
console.log(value);
}
Note that it is not guaranteed that every assignment to the store value will be logged. For example, in case of multiple synchronous assignments, some of them may be skipped due to the async nature of promises. However, it is always guaranteed that the last value will be logged.
Usage with React
You can use the following hook to bind to a store in a React component:
import {run} from 'abort-controller-x';
import {ReadonlyStore, watchStore} from 'abort-controller-x-reactive-store';
import {useEffect, useState} from 'react';
function useStoreValue<T>(store: ReadonlyStore<T>): T {
const [value, setValue] = useState(store.value);
useEffect(() => {
const stop = run(async signal => {
for await (const value of watchStore(signal, store)) {
setState(value);
}
});
return () => {
stop();
};
}, [store]);
return value;
}